Quantifiers
Quantifiers apply to the thing in front of them
/ax*a/ # aa, axa, axxa, axxxa, ... /ax+a/ # axa, axxa, axxxa, ... /ax?a/ # aa, axa /ax{2,4}a/ # axxa, axxxa, axxxxa /ax{3,}a/ # axxxa, axxxxa, ... /ax{17}a/ # axxxxxxxxxxxxxxxxxa
* 0- + 1- ? 0-1 {n,m} n-m {n,} n- {n} n